Tolerances of hybridized entomopathogenic nematode Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae) strains to heat and desiccation

Abstract

Heat and desiccation are two major problems of entomopathogenic nematodes (EPNs) for outdoor applications. The factors decrease their survival and effectivity in the field. Thus, the success ratio drops dramatically especially in hot and drought prone regions. Hybridization of EPNs is a way to overcome these major stress problems. In the present study, heat and desiccation tolerances of ten hybrid strains, which were hybridized from six domestic strains isolated from different climatic regions in Turkey, were determined. The heat tolerance experiments were performed at 32, 34, 36, 38, 40 and 42 °C and desiccation tolerance experiments were performed at PolyEthylene Glycol (PEG) concentrations of 10, 20, 30, 40, 50, 60, 70 and 80 %. The results of the tolerance experiments are shown as mean temperature tolerated by 50% of the population (MT) and mean temperature tolerated by 10% (MT) of the strains for heat testing, and as Lethal Concentration (LC and LC) for the desiccation test. For the heat tolerance experiments, the results showed that hybrid strains had slightly higher heat tolerance levels than their parents. In the desiccation experiments, it was determined that most of the hybrid strains had greater tolerances than their parents. The outcome of the study was promising for conducting further research and trials.

Keywords

• Heat, desiccation, hybrid, tolerance, Heterorhabditis bacteriophora

Hibrit entomopatojen nematod Heterorhabditis bacteriophora ırklarının yüksek sıcaklık ve su kaybına olan toleransları

Öz

Yüksek sıcaklık ve su kaybı, entomopatojen nematodların (EPN) açık alan uygulamalarındaki en büyük iki olumsuz faktördür. Bu faktörler, arazideki etkinliği ve hayatta kalma oranını düşürmekte ve bu nedenle özellikle sıcak bölgelerde zararlılara karşı başarı oranı ciddi oranda azalmaktadır. EPN’lerin hibridizasyonu, bu iki stres faktörünün önüne geçilmesinde önemli bir yöntemdir. Bu çalışmada, Türkiye’nin değişik coğrafik bölgelerinden izole edilen 6 farklı yerli ırktan hibritlenmiş 10 farklı hibrid ırkın yüksek sıcaklık ve su kaybına olan toleransları belirlenmiştir. Yüksek sıcaklık denemeleri 32, 34, 36, 38, 40 ve 42 ºC’lerde gerçekleştirilirken, su kaybı denemeleri PolyEthylene Glycol (PEG) adlı desikatörün % 10, 20, 30, 40, 50, 60, 70 ve 80 konsantrasyonlarında gerçekleştirilmiştir. Denemelerin sonuçları yüksek sıcaklık için popülasyonun % 50’sinin hayatta kalabildiği ortalama sıcaklık (MT) ve % 10’unun hayatta kalabildiği ortalama sıcaklık (MT) olarak belirtilmişken, su kaybı için lethal konsantrasyon (LC ve LC) olarak belirtilmiştir. Yüksek sıcaklık denemesinde hibrit ırkların sıcaklığa ebeveynlerinin biraz üzerinde tolerans gösterebildiği saptanırken, su kaybı denemesinde hibrit ırkların hemen hepsinin su kaybına ebeveynlerinden daha iyi tolerans gösterdiği belirlenmiştir. Bu çalışmada elde edilen sonuçlar, bu konuda yapılacak gelecek çalışmalar için ümit verici olarak görülmektedir.

Anahtar Kelimeler

• Yüksek sıcaklık, su kaybı, hibrit, tolerans, Heterorhabditis bacteriophora

References

1. Anbesse, S., N. H. Sumaya, A. V. Dörfler, O. Strauch & R-U. Ehlers, 2013. Selective breeding for desiccation tolerance in liquid culture provides genetically stable inbred lines of the entomopathogenic nematode Heterorhabditis bacteriophora. Applied Microbiology and Biotechnology, 97: 731-739.
2. Ehlers, R-U., 1996. Current and future use of nematodes in biocontrol: Practice and commercial aspects in regard to regulatory policies. Biocontrol Science Technology, 6: 303-316.
3. Ehlers, R-U., 2001. Mass production of entomopathogenic nematodes for plant protection. Applied Microbiology and Biotechnology, 56: 623-633.
4. Ehlers, R-U., 2003. “Biocontrol Nematodes, 177-220”. In: Environmental Impacts of Microbial Insecticides, (Ed: H. M. T. Hokkanen & A. J. Hajek). Kluwer Academic Publishers, Dordrecht, 270 pp.
5. Ehlers, R-U., J. Oestergaard, S. Hollmers, M. Wingen & O. Strauch, 2005. Genetic selection for heat tolerance and low temperature activity of the entomopathogenic nematode-bacterium complex Heterorhabditis bacteriophora - Photorhabdus luminescens. Biological Control, 50: 699- 716.
6. Gaugler, R. & H. Kaya, 1990. Entomopathogenic Nematodes in Biological Control. CRC Press, Boca Raton, FL, 365 pp.
7. Georgis, R., 1990. “Formulation and Application Technology, 173-191”. In: Entomopathogenic Nematodes in Biological Control (Ed: R. Gaugler & H.K. Kaya). CRC Press, Boca Raton, FL, 384 pp.
8. Glazer, I., R. Gaugler & D. Segal, 1991. Genetics of the nematode Heterorhabditis bacteriophora strain HP88: The diversity of beneficial traits. Journal of Nematology, 23: 324-333.

9. Grewal, P. S., S. Selvan & R. Gaugler, 1994. Thermal adaptation of entomopathogenic nematodes: Niche breadth for infection, establishment, and reproduction. Journal of Thermal Biology, 19: 245–253.
10. Johnigk, S. A., S. Hollmer, O. Strauch, U. Wyss & R-U. Ehlers, 2002. Heritability of the liquid culture mass production potential of the entomopathogenic nematode Heterorhabditis bacteriophora. Biocontrol Science and Technology, 12: 267–276.
11. Kaya, H. K. & R. Gaugler, 1993. Entomopathogenic nematodes. Annual Review of Entomology, 38: 181-206.
12. Koppenhöfer, A., 2000. “Nematodes, 309-315”. In: Field Manual of Techniques in Invertebrate Pathology ( Ed: L.A. Lacey & H.K. Kaya). Kluwer Academic Publishers, Dordrecht, 868 pp.
13. Lewis, E. E., R. Gaugler & R. Harrison, 1992. Entomopathogenic nematode host finding: response to host contact cues by cruise and ambush foragers. Parasitology, 105: 309–315.
14. Lunau, S., S. Stoessel, A. J. Schmidt-Peisker & R-U. Ehlers, 1993. Establishment of monoxenic inocula for scaling up in vitro cultures of the entomopathogenic nematodes Steinernema spp. and Heterorhabditis spp. Nematologica, 39: 385-399.
15. Mukuka, J., O. Strauch, M. H. Al Zainab & R-U. Ehlers, 2010a. Effect of temperature and desiccation stress on infectivity of stress tolerant hybrid strains of Heterorhabditis bacteriophora. Russian Journal of Nematology, 18: 111-116.
16. Mukuka, J., O. Strauch & R-U. Ehlers, 2010b. Variability in desiccation tolerance among different strains of the entomopathogenic nematode Heterorhabditis bacteriophora. Nematology, 12: 711-720.
17. Mukuka, J., O. Strauch, C. Hoppe & R-U. Ehlers, 2010c. Improvement of heat and desiccation tolerance in Heterorhabditis bacteriophora through cross-breeding of tolerant strains and successive genetic selection. BioControl, 55: 511-521.
18. Mukuka, J., O. Strauch, L. Waeyenberge, N. Viaene, M. Moens & R-U. Ehlers, 2010d. Heat tolerance among different strains of the entomopathogenic nematode Heterorhabditis bacteriophora. BioControl, 55: 423-434.
19. Peters, A., 1996. The natural host range of Steinernema and Heterorhabditis spp. and their impact on insect populations. Biocontrol Science and Technology, 6 (3): 389-402.
20. Shapiro, D. I., I. Glazer & D. Segal, 1996. Trait stability and fitness of the heat tolerant entomopathogenic nematode Heterorhabditis bacteriophora IS5 strain. Biological Control, 6: 238–244.
21. Somasekhar, N., P. S. Grewal & M. G. Klein, 2002. Genetic variability in stress tolerance and fitness among natural populations of Steinernema carpocapsae. Biological Control, 23: 303-310.
22. Strauch, O., I., Niemann, A., Neumann, A.J., Schmidt, A., Peters & R-U., Ehlers, 2000. Storage and formulation of the entomopathogenic nematodes Heterorhabditis indica and H. bacteriophora. BioControl, 45: 483–500.
23. Strauch, O., J. Oestergaard, S. Hollmer & R-U. Ehlers, 2004. Genetic improvement of the desiccation tolerance of the entomopathogenic nematode Heterorhabditis bacteriophora through selective breeding. Biological Control, 31: 218-2
24. Susurluk, A., I. Dix, E. Stackebrandt, O. Strauch, U. Wyss & R-U. Ehlers, 2001. Identification and ecological characterisation of three entomopathogenic nematode-bacterium complexes from Turkey. Nematology, 3: 833-8
25. Susurluk, A., 2008. Influence of temperature on the vertical movement of the entomopathogenic nematodes Steinernema feltiae (TUR-S3) and Heterorhabditis bacteriophora (TUR-H2), and infectivity of the moving nematodes. Nematology, 10: 137-141.
26. Wright, D. J., A. Peters, S. Schroer, & J. P. Fife, 2005. “Application Technology, 91-106”. In: Nematodes as Biological Control Agents (Ed: P.S. Grewal, R-U. Ehlers & D.I. Shapiro-Ilan). CABI Publishing, Wallingford, 528 pp.